The present invention relates to adaptive stepper motor control systems and more particularly to a method and apparatus for controlling the deceleration of a stepper motor in accordance with measured real time characteristics of the motor and load.
Stepper motors are controlled by the input signals or pulses, applied thereto and are frequently used to position a load. For example, a stepper motor can be used to position a machine tool, such as a milling machine, with respect to a piece of material to be worked upon by the machine tool. In many instances, it is very desirable that the position of the load be accurately controlled. This requires the rotation of the stepper motor to be accurately controlled by means of the drive signals applied thereto. Heretofore in the prior art, accurate positioning of a load by a stepper motor has been achieved to a certain extent by determining the deceleration characteristics of the stepper motor and load and then utilizing these characteristics to compute the deceleration required to stop the stepper motor when the load is moved from one position to another. One disadvantage to this is that the deceleration characteristic of the stepper motor and load does not remain constant over a period of time nor, in many instances, does the deceleration characteristics remain constant from one move to another. This can be alleviated to some extent by determining the deceleration characteristic of the motor and load more often. Obviously, however, this is cumbersome and not economical.
Accordingly, an object of this invention is to provide an improved method and apparatus for determining the deceleration characteristic of a stepper motor and load.
Another object of this invention is to provide an improved method and apparatus for determining the real time deceleration characteristics of a stepper motor and load.
Still another object of this invention is to provide an improved method and apparatus for controlling a stepping motor.
A further object of this invention is to provide an improved method and apparatus for controlling a stepping motor wherein, for every move greater than a predetermined distance, the real time deceleration characteristics are measured during the move and are utilized to calculate the deceleration that will be required to bring the motor to a stop at the desired location.